Hot melt adhesives

ABSTRACT

Polymers containing a high percentage of vinyl alcohol units may be blended with copolymers of alkyl methacrylates and unsaturated organic acids, the copolymers prefereably containing an adhesion-promoting functionality, the blend preferably containing low levels of a plasticizer to improve melt flow, and the blends in molten form utilized as hot melt adhesives for the bonding of wood, paper, and other celulosic articles.

This is a continuation-in-part of application Ser. No. 08/98,585, filedJul. 28, 1992, which is a continuation-in-part of application Ser. No.07/988,548, filed Dec. 10, 1992 which is a continuation-in-part ofapplication Ser. No. 07/872,478, filed Apr. 23, 1992 now abandoned.

FIELD OF THE INVENTION

This invention relates to blends, especially melt-processable blends, ofpolymers containing a high percentage of vinyl alcohol units blendedwith certain copolymers of alkyl methacrylates with unsaturated organicacids, such as methacrylic acid. It further relates to blends,especially melt-processed blends of these polymers in the form of sheet,film, fibers and other formed objects which exhibit a useful balance ofbarrier and strength properties, such as good resistance to permeationof gases, low moisture absorptivity, and toughness/modulus balanceadequate for packaging uses.

BACKGROUND OF THE INVENTION

Of all the synthetic polymers considered as materials with useful gaspermeation properties, such as resistance to passage of oxygen, carbondioxide, water, and the like, poly(vinyl alcohol) (PVOH), a polymer madeup of units of the structure ##STR1## and generally prepared by thetotal hydrolysis of homopolymers of vinyl acetate or related vinylesters, the starting polymer made up of units of the structure ##STR2##where R is alkyl, that is, from one to eight carbon atoms, preferablymethyl, ranks as the most impervious to the passage of small molecules.PVOH exhibits this property because of the high cohesive energy densityand polarity of the hydroxyl groups. The presence of the network ofhydroxyl groups has the concomitant effect of rendering the polymer(PVOH) impermeable to gases, but sensitive to moisture. The strongintermolecular interaction resulting from the high polarity of the --OHfunctional group gives rise to a melting temperature in the vicinity ofthe degradation temperature of PVOH. Consequently, melting isaccompanied by degradation. The degradation is so severe that PVOH byitself cannot either be melt extruded or injection molded.

The above limitations were surmounted by the preparation and subsequenthydrolysis of vinyl acetate copolymers with monomers other than vinylesters, especially copolymers with olefins, such as ethylene, propylene,butene-1, and the like. Hydrolysis of ethylene/vinyl acetate copolymersprovides a polymer which exhibits those desirable characteristics ofPVOH, but is superior to PVOH in performance in hydrophilicenvironments, such as wet strength, and in melt processability. However,these copolymers exhibit a significant increase in the permeability ofthe polymer to small molecules. Polymers having a low mol percentage ofethylene, such as from about 5 to about 25 mol percent, are similar topoly(vinyl alcohol) in that they cannot be melt-processed into filmwithout the aid of plasticizers.

In order to render PVOH melt processable, steps have been taken to breakup the crystallinity by the addition of external plasticizers. Amongstthe best known plasticizers of PVOH are the polyols; these includepolyethylene glycol, glycerol, and neopentyl glycol. The use of smallmolecules or oligomers as plasticizers for PVOH has its inherentlimitations and disadvantages. The current state of the art technologyemploys 10-25 parts of plasticizer to 100 parts of PVOH. A higherconcentration of plasticizer leads to phase separation and embrittlementof the plasticized matrix. Low levels of plasticizer, on the other hand,lead to the formation of highly viscous inextrudable melts during meltprocessing and extrusion. Another shortcoming of plasticized PVOH is theoccurrence of plasticizer migration, which arises during thermalprocessing such as extrusion and heat sealing of PVOH film. Duringextrusion, the low molecular weight plasticizer may deposit at the dielips. During heat sealing, the low molecular weight plasticizer willmigrate and evaporate from the heated region of the film. In the absenceof the plasticizer, the PVOH rapidly recrystallizes and embrittles theheat sealed portion of the film. In a packaging application, thisembrittlement can compromise the integrity of the package via cracks andpinholes. Another shortcoming of externally plasticized PVOH, whichmanifests itself when the plasticized PVOH resin comes into contact withalkaline or acidic solvents, is the hydrolysis and subsequentembrittlement of the partially hydrolyzed PVOH resin that is frequentlyused in preparing plasticized PVOH material.

Preparation of internally plasticized PVOH resin by polymerization ofvinyl acetate in the presence of a plasticizer or second polymer hasbeen studied to overcome the above difficulties, but suchpolymerizations, especially in emulsion, offer limitations caused by thedifficulty of dispersing the plasticizer or pre-formed second polymerwhere it is intimately admixed with the polymerizing vinyl ester, whichhas a significant degree of water solubility.

In spite of the fact that all of the above mentioned techniques have theeffect of improving the melt processing characteristics of PVOH, theyalso have the concomitant effects of significantly increasing thepermeability of the resin to small molecules and reducing the stiffnessand heat distortion temperature of the resin. Thus there exists a needfor a means to allow melt-processing of polymers of high vinyl alcoholcontent, such as fully hydrolyzed or highly hydrolyzed polymers of vinylesters, into useful objects maintaining most of the barrier propertiesof the polymer of high vinyl alcohol content. There further exists aneed for additive polymers which may be blended with polymers of highvinyl alcohol content to enhance their ability to form films andcoatings with improved properties of the film or coating without muchloss in barrier properties.

In U.S. patent application Ser. No. 07/781,715, which has the sameinventors and the same assignment as the present application, aredisclosed additive polymers useful in allowing melt processing of thepoly(vinyl alcohol) materials discussed above without significantalteration of their physical and barrier properties. These additivepolymers are copolymers of lower alkyl methacrylates with a variety ofnitrogenous monomers, especially those bearing amide groups, and mostespecially N-vinylpyrrolidone. Further is disclosed as more usefuladditives terpolymers containing lower alkyl methacrylates, the samenitrogenous co-monomers, and copolymerized unsaturated carboxylic acids,such as methacrylic acid. It is further disclosed that these latterterpolymers form segmented copolymers on blending with the poly(vinylalcohol) matrix polymers.

The polymers of application Ser. No. 781,715 do require nitrogenousmonomers, which adds to the cost, which are somewhat difficult toincorporate effectively by emulsion copolymerization, and which maycontribute color to the resulting blends. For these and other reasons,it would be desirable to remove the nitrogenous monomers if similarresults in blends with poly(vinyl alcohol) can be retained.

In U.S. Pat. No. 5,010,134, Chiang et al. disclose graft copolymers ofpoly(vinyl alcohol) with copolymers of 30-90 mol % methyl methacrylateand 10-70 mol % maleic anhydride, which graft copolymers areinsolubilized upon heating to the processing temperatures of the presentinvention, so that the blends are not useful as thermoplastics, and arenot melt-processable.

SUMMARY OF THE INVENTION

As is well known in the polymer art, polymers differ in chemicalstructure from the monomers from which they are made. One can refer to apolymer of methyl methacrylate or poly(ethylene glycol terephthalate),but it is not exactly correct to refer to a polymer containing methylmethacrylate or a polymer containing ethylene glycol and terephthalicacid. Thus we have chosen to use the term "units derived from", such asa polymer containing units derived from methyl methacrylate or unitsderived from an aliphatic diol and an aromatic dicarboxylic acid. It isbelieved that this accurately represents the composition of the polymerwhich otherwise requires a complicated IUPAC nomenclature or a series offormulas.

We have found a melt-processable polymeric blend comprising:

a) from about 70 to about 98 parts of a first polymer containing atleast about 50 mol percent of units of the structure ##STR3## andoptionally units of the structure ##STR4## wherein R is alkyl, that is,of one to eight carbon atoms, R₁ is H or CH₃, and R₂ is an alkyleneoxyor a C₁ to C₄ alkyl group, such as ethyl, methyl, n-butyl, iso-butyl,and the like; and

b) from about 2 to about 30 parts of a second polymer containing fromabout 75 to about 98 weight percent of units of the structure ##STR5##where R₃ is lower alkyl of from 1 to 4 carbon atoms such as methyl,ethyl, propyl, or butyl, and from about 2 parts to about 25 parts ofunits derived from an unsaturated copolymerizable unsaturated acid, theacid preferably of the structure ##STR6## where R₄ is --COOH.

In one desired component of the invention, the polymeric blend is onewherein the first polymer comprises at least about 95 mol, morepreferably about 99, mol percent of units of the structure ##STR7## andwhere the second polymer comprises from about 80 to about 90 weightpercent of units of the structure ##STR8## where R₁ and R₃ are --CH₃.This is desired because of the best balance of processing and propertiesof the blends.

If an alkeneoxy group is present, it is preferred the alkeneoxy groupcontain from 1 to about 20 alkeneoxy units and terminate in hydrogen, aC₁ -C₂₀ alkyl, C₆ aryl, or C₇ -C₂₀ alkaryl group.

We have found that a carboxylic acid anhydride unit formed in situ in apolymer mainly of lower alkyl methacrylate units will also impartthermoprocessable properties to the poly(vinyl alcohol). Specifically,poly(methyl methacrylate) can be treated by the method ofHallden-Abberton, et al., U.S. Pat. No. 4,874,824, with dimethylamine inan extruder to form a polymer containing from about 2 to about 25 weightpercent of glutaric anhydride units, i.e. ##STR9##

The resulting copolymer may be combined at levels of from about 2 toabout 30 parts of the glutaric anhydride units with from 70 to 98 partsof the above-listed poly(vinyl alcohol) homo- and copolymers to form amelt-processable blend.

It has also been discovered that styrene polymers containing acid and/oranhydride functionality may also be utilized to modify favorably themelt processing of poly(vinyl alcohol). More specifically, we havediscovered a melt-processable polymeric blend comprising:

a) from about 80 to about 98 parts of a first polymer containing atleast about 50 mol % units of the structure ##STR10## and optionallyunits selected from one or more of the following structures: ##STR11##wherein R is alkyl, R₁ is H or CH₃, and R₂ is an alkyleneoxy group; and

b) from about 2 to about 20 parts of a second polymer containing fromabout 60 to about 98 weight percent of units of the structure ##STR12##where Ar is aryl, halogen-substituted aryl, or alkyl-substituted aryl,and where R₅ is --H or --CH₃ and from about 2 to about 15 weight percentof units derived from an unsaturated copolymerizable carboxylic acid oranhydride. The second polymer may further contain up to about 25 weightpercent of methacrylonitrile or acrylonitrile. Such polymers includecopolymers of styrene/maleic acid, styrene/maleic anhydride,styrene/methacrylic acid, styrene/α-methylstyrene/acrylic acid,styrene/α-methylstyrene/methyl methacrylate/methacrylic acid,styrene/methyl methacrylate/methacrylic acid, styrene/citraconic acid,styrene/butadiene/methacrylic acid, styrene/acrylic acid/maleicanhydride, and the like.

Although not a carboxylic acid, copolymers of an unsaturated sulfonicacid with vinyl aromatic monomers may be employed, such as a copolymerof styrene with styrene sulfonic acid.

We have also found that useful articles may be made from these blends,when they are processed in the form of a foil, sheet, film, fiber,packaging material, multilayer laminate, or molded article.

We have also found that some chemical interaction between the componentsoccurs during the blending/processing operation, and so we havediscovered a melt-processable thermoplastic segmented polymer comprisingfrom about 70 to about 98 parts of at least one segment of a firstpolymer containing at least 50 mol percent units of the structure##STR13## and optionally units of the structure ##STR14## wherein R isalkyl, R₁ is H or CH₃, and R₂ is an alkyleneoxy group; and chemicallyjoined thereto from about 2 to about 30 parts of at least one segment ofa second polymer containing from about 75 to about 98 weight percent ofunits of the structure ##STR15## where R₃ is lower alkyl, and from about2 to about 25 weight percent of units derived from an unsaturatedcopolymerizable carboxylic acid or anhydride. A preferred composition isone wherein at least one first polymer segment contains more than about85 mol percent of units of the structure ##STR16## and wherein at leastone first polymer segment is from about 70 to about 90 parts by weightof the segmented polymer. This composition is preferred because of thebest balance of processing and properties of the of the segmentedcopolymer.

DETAILED DESCRIPTION OF THE INVENTION

The blends of the vinyl alcohol polymers and the(meth)acrylate/copolymerized acid polymers may be formed into usefulobjects by many techniques, including casting from solution, compressionmolding of powder blends, formation of films and sheets from mixtures oflatices and water-soluble polymers, extrusion of melt blends, and thelike. The scope of the invention is not limited by the means ofprocessing.

However, the major advantage of the invention is that the blends can bemelt-processed under practical conditions under which the vinyl alcoholalone is non-processable. By melt-processable is meant that the polymeror blend can be converted from a solid form such as pellets, powder, andthe like into a thermoplastic viscoelastic melt within an extruder orother heating/mixing device, that the melt is thermally stable enough toresist thermal degradation, and that the melt can be processed byextrusion, calendering, laminating, molding and the like into usefulobjects. The malt will neither be so liquid that it cannot be containedwithin the extruder or cannot be issued from the extruder in solid form,nor will it be so viscous that the extruder is incapable of processingit without damage to the equipment, nor will it be so thermally unstablethat degradation will spoil the appearance or physical properties ofobjects processed from the melt. Further, the melt and resultingextrudate must be uniform in appearance. Further, thermoplastic impliesthat the material may be re-processed by a similar operation into usefulobjects having about the same physical and chemical properties as thoseobtained from the first thermoplastic processing of the blend.

The first polymer of the blend, which we shall designate PVOH, is ahomopolymer or a copolymer of "vinyl alcohol" and a vinyl ester. Vinylalcohol does not exist in monomeric form, and polymers containing suchunits must perforce be derived by chemical alteration of polymersderived from another monomer. The most common means of preparing suchpolymers is to polymerize a vinyl ester, such as vinyl formate, vinylacetate, and the like of the structure ##STR17## where R is H or alkyl,which we define as aliphatic carbon chains of from 1 to 20 carbons,preferably 1 to 8, and most preferably 1, the chains being linear,branched, or cyclic. Thus, most preferred is vinyl acetate, where R is--CH₃. Such polymers may be almost completely saponified or hydrolyzedto form polymers of greater than 99 mol % "vinyl alcohol". A smallnumber of units derived from the unhydrolyzed vinyl ester may bepresent. By controlling the conditions of hydrolysis or saponification,copolymers of the vinyl ester and vinyl alcohol may be formed. A rangeof such compositions are commercially available. The range of from about50 mol % to about 100 mol % of vinyl alcohol is encompassed in theinvention. Other co-monomers may be present in the first polymer, but atlow molar levels, such as below about 10 mol %. Such co-monomers mayinclude (meth)acrylic esters, such as alkyl esters, such as ethylacrylate, butyl methacrylate, and the like, hydroxyalkyl(meth)acrylates, such as betahydroxyethyl methacrylate, and the like,olefins, such as ethylene, propylene, butene-1 and the like, vinylhalides, such as vinyl chloride, N-vinyllactams, maleic anhydride,dialkyl maleates, dialkyl fumarates, and the like. Of the olefins whichmay be copolymerized, having the formula

    CH.sub.2 ═CHR or CH.sub.2 ═CH.sub.2

it is preferred that ethylene be used. As noted, most commercialcopolymers of ethylene and vinyl alcohol, having a relatively low mol %of vinyl alcohol content and diminished barrier properties, areunsuitable for the purposes of the present invention; however,copolymers of from about 5 to about 25 mol percent ethylene, preferablyfrom about 5 to about 15 mol percent, may be melt-processed when blendedwith the copolymers of lower alkyl (meth)acrylates disclosed herein.

The partially or totally hydrolyzed PVOH which may be employed in thisinvention possess a molecular weight (weight average) between 13,000 and2,000,000, but preferably between 31,000 and 50,000 since in thismolecular weight range the PVOH processes more readily in the presenceof the additive polymer. The viscosity of these two ranges of averagemolecular weights may also be measured in solution, and will vary from3-50 cPs (4 % aqueous solutions, 20° C.), preferably between 22-26 cPs.If PVOH of a higher degree of saponification (87-99.9 mol %) isutilized, the PVOH polymer may be of higher molecular weight, to as highas about 2,000,000.

The first polymer may also contain units derived from alkyleneoxy(meth)acrylates, such as are described in U.S. Pat. No. 4,618,648,incorporated herein by reference. Such alkyleneoxy (meth)acrylates areesters of (meth)acrylic acid having as the "alcohol" portion oligomersof --CH₂ --CHY--O-- units, where Y is hydrogen or methyl, and arederived from oligomerization of ethylene and/or propylene oxide. Theymay be terminated at one end by alkyl, aryl, or alkaryl groups, such asC₁ -C₂₀ alkyl, C₆ aryl or C₇ -C₂₀ alkaryl group. The formula may beexpressed as ##STR18## where R₁ and R₃ are as defined above.

The second component of the melt-processable blend is a polymer which isa copolymer of from about 75 to 98 parts of a C₁ to C₄ alkyl ester ofacrylic or methacrylic acid, preferably the C₁ ester of methacrylicacid, which is methyl methacrylate, with from about 2 to about 25 partsof an unsaturated copolymerizable carboxylic acid, the acid preferablyof the structure ##STR19## where R₄ is --COOH. Such acids includeacrylic acid, methacrylic acid, maleic acid, fumaric acid, maleicanhydride, itaconic acid, monoalkyl maleates, monoalkyl fumarates,monoalkyl itaconates, acryloxypropionic acid, and the like. Acids suchas vinylbenzoic acid, allyloxyacetic acid, and the like may also beemployed. Copolymerizable anhydrides, such as maleic anhydride anditaconic anhydride are also effective in the practice of the invention.Acid/anhydride groups from post-polymerization reactions may also beused, such as acid groups introduced by the pyrolysis to t-butyl esters,such as those of units derived from t-butyl methacrylate, or by treatingan ester-containing polymer with dimethylamine, as taught inHallden-Abberton, U.S. Pat. No. 4,874,824. Of the acids, especiallypreferred for cost and ease of incorporation is methacrylic acid.

Other monomers may be copolymerized with those listed above whichcomprise the second copolymer, as long as they do not adversely affecteither the copolymerization behavior, the processing of the blends, orthe physical properties of the blend. Such monomers include up to about10 parts of vinyl esters, such as vinyl acetate, vinyl aromatics, suchas styrene, other esters of (meth)acrylic acid, such as glycidylmethacrylate, 2-ethylhexyl acrylate, and the like, (meth)acrylonitrile,and the like.

It is possible to use the acid- or anhydride containing polymer in theform of a multi-stage or core/shell polymer. Such polymers arewell-known as impact modifiers for a variety of matrix polar plastics,especially when the matrix polymer contains groups to bond with the acidor anhydride. Thus polymers such as taught by Owens et al., U.S. Pat.No. 3,668,247, are useful in thermoprocessable blends of the presentinvention.

More specifically, the invention encompasses a melt-processablepolymeric blend comprising:

a) from about 80 to about 98 parts of a first polymer containing atleast about 50 mol % units of the structure ##STR20## and optionallyunits selected from one or more of the following structures: ##STR21##wherein R is alkyl, R₁ is H or CH₃, and R₂ is an alkyleneoxy group; and

b) from about 2 to about 20 parts of a second, core/shell, polymercomprising:

1. a rubbery cross-linked core polymer which contains greater than 75weight percent, based on total weight of the core, of butadiene and/orone or more C₂ -C₈ alkyl esters of acrylic acid;

2. a shell polymer containing from about 90 to about 98 weight percentof units of the structure ##STR22## where R₁ is CH₃, and R₃ is C₁ -C₄lower alkyl, and from about 2 to about 10 weight percent of unitsderived from an unsaturated copolymerizable carboxylic acid oranhydride. Preferred are such compositions wherein the core polymer isat least 60% by weight of the core/shell polymer, and wherein theoptional unit of the first polymer is ##STR23## R_(l) and R₃ are --CH₃,R₅ is --H and the unsaturated copolymerizable unsaturated acid has oneof the following structures: ##STR24## where R₄ is --COOH. Especiallypreferred is wherein the first polymer comprises at least about 95 molpercent, preferably greater than about 98% of units of the structure##STR25## and wherein the second polymer comprises from about 2 to about10 weight percent of units derived from the unsaturated carboxylic acidof the structure

    CH.sub.2 ═C(CH.sub.3)R.sub.4.

Such blends may be prepared in the form of a foil, sheet, film, fiber,packaging material, multi-layer laminate or molded article.

It appears that such acid-containing methacrylic ester polymers, whenpolymerized in the presence of a polyolefin, are ineffective in forminga melt-processable blend with poly(vinyl alcohol).

It is also possible to use the acid- or anhydride containing vinylaromatic polymer in the form of a multi-stage or core/shell polymer.More specifically, the invention encompasses a melt-processablepolymeric blend comprising:

a) from about 80 to about 98 parts of a first polymer containing atleast about 50 mol % units of the structure ##STR26## and optionallyunits selected from one or more of the following structures: ##STR27##wherein R is alkyl, R₁ is H or CH₃, and R₂ is an alkyleneoxy group; and

b) from about 2 to about 20 parts of a second, core/shell, polymercomprising:

1. a rubbery cross-linked core polymer which contains greater than 75weight percent, based on total weight of the core, of butadiene and/orone or more C₂ -C₈ alkyl esters of acrylic acid;

2. a shell polymer containing from about 50 to about 98 weight percentof units of the structure ##STR28## where Ar is aryl,halogen-substituted aryl, or alkyl-substituted aryl, where R₅ is --H or--CH₃, optionally up to about 30 weight percent of units derived from(meth)acrylonitrile, and from about 2 to about 25 weight percent ofunits derived from an unsaturated copolymerizable carboxylic acid oranhydride.

It appears that such acid-containing vinyl aromatic polymers, whenpolymerized in the presence of a polyolefin, are ineffective in forminga melt-processable blend with poly(vinyl alcohol).

We further envisage a melt-processable polymeric blend comprising:

from about 80 to about 98 parts of a first polymer containing at leastabout 50 mol units of the structure ##STR29## and optionally unitsselected from one or more of the following structures: ##STR30## whereinR is alkyl, R₁ is H or CH₃, and R₂ is an alkyleneoxy group; and fromabout 2 to about 20 parts of a second, multi-stage, polymer comprising:

1. a rubbery cross-linked first stage polymer which contains greaterthan 75 weight percent, based on total weight of the first stage ofbutadiene and/or one or more C₂ -C₈ alkyl esters of acrylic acid, thefirst stage polymer further containing from about 0.5 to about 5 weightpercent, of units derived from an unsaturated carboxylic acid;

2. a second-stage polymer containing from about 50 to about 100 weightpercent of units of at least one of the structures ##STR31## where Ar isaryl, halogen-substituted aryl, or alkyl-substituted aryl, where R₅ is--H or --CH₃, and optionally up to about 10 weight percent of unitsderived from an unsaturated carboxylic acid.

Such polymers are not necessarily core/shell polymers, as the secondstage may be as domains included in the first stage, similar inmorphology to polymers described in U.S. Pat. No. 4,184,373.

These multi-stage polymers, especially when an alkyl acrylate is in thefirst stage and a vinyl aromatic monomer in the second stage, whencombined with poly(vinyl alcohol) and with additive polymers which arecopolymers of an alkyl methacrylate and an anhydride or carboxylic acid,or preferably, with an additive terpolymer of an alkyl methacrylate, amonomer containing lactam or amide functionality and an acid group, givea ternary blend which exhibits melt processability and improved tensilestrength and toughness.

The preferred additive terpolymer is a methyl methacrylate/N-vinylpyrrolidone/methacrylic acid terpolymer. Such polymers are described inallowed U.S. patent application Ser. No. 781,715, herein incorporated byreference.

Thus, we envisage a melt-processable ternary polymeric blend comprising:

from about 55 to about 90 parts of a first polymer containing at leastabout 50 mol units of the structure ##STR32## and optionally unitsselected from one or more of the following structures: ##STR33## whereinR is alkyl, R₁ is H or CH₃, and R₂ is an alkyleneoxy group; from about 5to about 30 parts of a second, multi-stage, polymer comprising:

1. a rubbery cross-linked first stage polymer which contains greaterthan 75 weight percent, based on total weight of the first stage, ofbutadiene and/or one or more C₂ -C₈ alkyl esters of acrylic acid, thefirst stage polymer further containing from about 0.5 to about 5 weightpercent, of units derived from an unsaturated carboxylic acid;

2. a second-stage polymer containing from about 50 to about 100 weightpercent of units of at least one of the structures ##STR34## where Ar isaryl, halogen-substituted aryl, or alkyl-substituted aryl, where R₅ is--H or --CH₃, and optionally up to about 10 weight percent of unitsderived from an unsaturated carboxylic acid; and

from about 5 to about 15 parts of a third polymer containing from about5 to about 25 weight percent of units of the structure ##STR35## whereinn is 2, 3, 4 or 5, R₆ and R₇ may be the same or different and are H-, C₁-C₄ alkyl, or --C₂ H₄ --(O--C₂ H₄)-- in a cyclic form, and where R₈ is aurea or cyclic ureido structure of the formula ##STR36## from about 94to about 4 weight percent of units of the structure ##STR37## wherein R₂is C₁ -C₄ alkyl; and from about 1 to about 10 weight percent of acopolymerizable unsaturated acid, anhydride or glycidyl-containingester.

It is further possible to modify the poly(vinyl alcohol) polymers tomake them melt-processable by preparing blends with acid- oranhydride-containing polymers which are copolymers with other vinyl orvinylidene divinyl monomers.

Thus, we envision a melt-processable polymeric blend comprising:

a) from about 80 to about 98 parts of a first polymer containing atleast about 50 mol % units of the structure ##STR38## and optionallyunits selected from one or more of the following structures: ##STR39##wherein R is alkyl, R₁ is H or CH₃, and R₂ is an alkyleneoxy group; and

b) from about 2 to about 20 parts of a second polymer containing fromabout 60 to about 98 weight percent of units of the structures

    CH.sub.2 ═CR.sub.1 CN; CH.sub.2 ═CHCl; CH.sub.2 ═C(Cl).sub.2 ; CH.sub.2 ═CH--O--C(O)R; CH.sub.2 ═CH--O--R; CH.sub.2 ═CH --Pyr; CH.sub.2 ═CR.sub.1 R.sub.5 ; CH.sub.2 ═C(Cl)--CH═CH.sub.2 ; or CH.sub.2 ═CH--CR.sub.1 ═CH.sub.2

where Pyr is pyridinyl or alkyl-substituted pyridinyl, and from about 2to about 15 weight percent of units derived from an unsaturatedcopolymerizable carboxylic acid or anhydride. Such monomers includecopolymers containing one or more of such monomers as isobutylene,ethylene, propylene, chloroprene, butadiene, isoprene,(meth)acrylonitrile, vinyl chloride, vinylidene chloride, vinyl esters,such as vinyl acetate, vinyl ethers, vinyl pyridine,2-vinyl-5-methylpyridene, and the like. Such polymers with levels ofcarboxylic acid or anhydride from about 2 to about 15 weight percent,include poly(acrylonitrile-methyl acrylate-itaconic acid),ethylene-(meth)acrylic acid/fumaric acid/itaconic acid/maleic anhydridecopolymer, poly(butadiene-acrylonitrile-methacrylic acid) terpolymer,isobutylene-maleic acid copolymer, vinyl chloride-vinylacetate-unsaturated dibasic acid terpolymer, chloroprene-acrylic acidcopolymer, acrylonitrile-alpha, beta-unsaturated carboxylic acidcopolymer, poly(vinyl ether-maleic acid) copolymer, poly(vinylacetate-crotonic acid) copolymer, isoprene-unsaturated carboxylic acidcopolymer, poly(methyl vinyl ether-maleic acid) copolymer,poly((meth)acrylate-vinyl acetate-dicarboxylic acid) terpolymer,poly(ethylene-ethyl acrylate-maleic anhydride) terpolymer,poly(methacrylic acid-ethyl acrylate-methacrylamide),poly(isobutylene-methacrylic acid/anhydride) copolymer, poly(acrylicacid-2 methyl-5-vinyl pyridine) copolymer, poly(vinylidenechloride(meth)acrylic acid) copolymer, poly(ethylene-vinylacetate-maleic anhydride) terpolymer, poly(vinyl chloride-vinylacetate-maleic anhydride) terpolymer, and the like.

It is believed that the acid group present in the second copolymerparticipates in a chemical reaction with the poly(vinyl alcohol) toproduce a segmented copolymer of the structure described above. Apreferred embodiment of this segmented copolymer comprises a segmentedcopolymer wherein the trunk contains more than about 85 mol percent ofunits derived from vinyl alcohol, wherein the grafted or side-chainpolymer contains from about 2 to about 25, preferably about 10 to about20 parts by weight, of units derived from an unsaturated carboxylic acidor anhydride, the remainder being of units derived from methylmethacrylate, and wherein the trunk polymer is from about 70 to about 90parts by weight of the graft copolymer.

The above description is based on an expected combination of the twopolymers in weight ratios similar to those in the original ungraftedblend. However, it is quite possible that selected grafting will occur,so that the graft copolymer may contain more or less of the trunkcomponent than in the original blend.

Even if grafting is not accomplished, the additives of the presentinvention improve the internal and external plasticization of the vinylalcohol-containing polymers, probably by compatibilization throughdipole-dipole and hydrogen-bonding interaction between appropriatefunctional groups. Such plasticization allows for the compounder toprocess the polymer above the melting point and below the decompositiontemperature. Additional plasticizer may be added for improvedprocessing, if desired.

The extent of grafting may be enhanced by the presence of catalysts foresterification reactions between acid or anhydride groups and alcoholgroups, or by catalysts for reaction of epoxy groups with acid groups.Such catalysts may include acids, bases, organotin catalysts,organotitanium catalysts, and the like. The esterification reaction maybe enhanced also by removal of water formed during the graftingreaction, such as by vacuum application to the reactor, such as a vacuumvent on the extruder. It is, of course, important that the reaction notbe pushed to the point where the graft polymer becomes an intractablematerial which cannot be melt-processed.

The second copolymer may be prepared by any of the methods known to theart, such as in bulk, suspension, solution, and the like. Preferred forease of polymerization, availability of higher molecular weights, andease of isolating into powdery form, is emulsion polymerization. Theweight-average molecular weight of the second polymer may vary fromabout 10,000 to about 500,000; preferred for ease of processing, thermalstability, and rheological properties is from about 10,000 to about200,000. However, when the first polymer is of relatively high molecularweight, the preferred molecular weight range of the second polymer isfrom about 200 to about 100,000. Such low molecular weight polymers oroligomers may be made by several known methods, such asalkoxide-initiated polymerization of methyl methacrylate followed bypartial hydrolysis, thermal dimerization of methylmethacrylic/methacrylic acid mixtures, and the like. By following theexperimental procedures described below, the skilled practitioner canreadily determine if appropriate melt strength has been achieved withoutraising the melt viscosity to the extent that processing and extrusionare difficult.

A compositional range of from about 80 to about 98 parts of the firstpolymer and correspondingly from about 2 parts to about 20 parts of thesecond polymer is contemplated. Below about 2 parts of the additive, thethermal stability is not greatly improved and the blends are yellow;above about 25 parts, the additive polymers do not disperse well andsome diminution of properties, such as extensibility and impactstrength, is seen. Preferred is about 10 to about 20 parts of theadditive. The less of the additive required to achieve meltprocessability, the better will desirable PVOH properties, such asoxygen barrier, be maintained. Preferred for water-dispersible films asthe first polymer is a copolymer of vinyl acetate hydrolyzed orsaponified to a degree to retain from about 5 to about 13 mole % ofvinyl acetate units. For certain properties such as barrier to gases, itis preferred that first polymer be essentially fully hydrolyzed.

The (meth)acrylate copolymers used in this invention were prepared byemulsion polymerization of commercially available acrylic or methacrylicesters, such as methyl methacrylate, with the unsaturated carboxylicacid. Levels of carboxylic acid, especially when the acid is acrylicacid, tend to give difficulties in emulsion polymerization, theresulting polymer being somewhat water-soluble. Other suitably adaptedpolymerization methods such as solution, suspension, or bulkpolymerization may also serve to prepare the copolymers.

As noted, when the second polymer contains units derived from anunsaturated acid or anhydride, chemical attachment frequently occursbetween the first and second polymers under processing conditions. Thesechemically joined polymers are defined as segmented polymers, where atleast one segment of the first polymer as defined above is chemicallyjoined to at least one segment of the second polymer. Since both typesof segment have, prior to chemically joining, more than one reactivegroup, at this stage of investigation, it is difficult to describe thestructure of the segmented polymer in conventional "graft copolymer"terminology. Depending on the relative amounts of first and secondpolymers and the extent of reaction, it is difficult to state whichpolymer is the trunk and which the graft.

Graft copolymers with poly(vinyl alcohol) trunks and(meth)acrylate-based grafts or side chains have been known for manyyears, and may be prepared by use of cerium (+IV) catalysts to formradical sites on the poly(vinyl alcohol) and then to initiatepolymerization of the (meth)acrylate monomers from these sites. However,there has been no disclosure that prior art graft polymers arethermoplastic or melt-processable.

The additive polymer may be a ter- or tetrapolymer containing acid unitsfrom more than one acid or anhydride, and containing more than more thanone (meth)acrylate ester units. Such ter- or tetrapolymers, especiallythose with a lower alkyl acrylate ester copolymerized, have somewhatlower softening temperatures, within the vicinity of the glasstemperature of the amorphous phase of the polymer containing vinylalcohol units, so that melt blending is easier to control, without asignificant decrease in physical properties of the blend.

The first polymer may be a blend of more than one polymer containingvinyl alcohol units, such as those of differing molecular weight.

The first polymer, containing vinyl alcohol units, may be washed or beneutralized with acid such as phosphoric acid to remove residual sodiumacetate, as taught in U.S. Pat. No. 3,425,979. The art teaches thatsodium acetate from the alkaline hydrolysis of the copolymerized vinylacetate accelerates the formation of conjugated species and chemicalcross-links upon heating the polymer containing vinyl alcohol units towithin a few degrees of its melting temperature. Washing to lower thelevel of sodium acetate to below about 0.1 weight percent, or treatmentwith an acid such as phosphoric acid, whose sodium salt is notdeleterious to degradation of the polymer containing vinyl alcoholunits, produces a polymer of enhanced thermal stability which allowsmore flexibility in the choice of blending conditions of the acrylicadditive in the melt-processable blend. When the acid treatment is used,the acetic acid formed is removed in the extrusion process byappropriate venting. In both treatments, essentially all of the sodiumacetate is removed, so that the content of sodium acetate is less thanabout 0.1 wt. percent, based on the polymer containing vinyl alcohol.

Blending of the two copolymers may be carried out most conveniently bydry mixing the finely granulated polymer particles prior to meltcompounding in a single- or twin-screw extruder. In the process of dryblending, small quantities of additives may be added to the mixture ofparticulates for the purpose of improving the physical properties of theblend. Examples of additives may include one or more of the followingclasses of compounds: antioxidants, ultraviolet light absorbers,plasticizers, antistatic agent, slip agents, coloring agents, fillersand other compounds. Further, fugitive plasticizers, such as water inamounts about 3%, may be added to aid in compounding and processing theblend.

The blend may further be prepared by admixing the additive polymer inemulsion form, when an emulsion polymerization is a feasible way toprepare the additive polymer, with the poly(vinyl alcohol) in solidform, and then processing directly with water removal such as byextrusion in a vented extruder, or by drying the powder blend undervacuum, and then blending with the matrix polymer.

The blend may further contain glycerol in small amounts. Althoughglycerol may lower the glass temperature of the final blend, it can aidin obtaining better admixture of the two components, so as to avoidpresence of gel or requirement of extensive melt-mixing.

The blend may further contain impact modifiers known to the art, such asmultistage polymers based on a poly(acrylate) first stage or apolybutadiene first stage and a methacrylate or styrene second stage,which may be present as a shell or in separate domains within the core.Either stage may contain acid-functional groups.

The blends of the present invention may be considered as a polymercontaining vinyl alcohol units modified with a processing aid, since theacrylic copolymer additive enables the poly(vinyl alcohol) to bemelt-processed with a reduced tendency towards thermal decomposition,and aids in the formation of melt-processable objects ormelt-processable intermediates, such as pellets.

The blends of the present invention, especially those which aremelt-processable, are useful in many applications. When the vinylalcohol polymer is water-soluble, a film from the blends can be brokendown in water for ready disposal. Such blends in film form may also beuseful as containers for toxic, corrosive, or skin-sensitizing chemicalswhich are to be used in water, such as agricultural chemicals to besprayed. The blends in film form such as in blown film, are useful ashigh gas barrier films for packaging, especially of food. The films fromthe blends can be laminated onto substrates to form useful barrierstructures for containment or packaging of food or beverages. The blendsin container form, such as film, bottles, and the like may be used toexclude gases such as oxygen or to contain gases such as carbon dioxide.Blends with improved heat distortion properties may be useful in hotfill packaging or in retortable or sterilizable container packaging. Theblends or laminates may also be useful in museum and other glazing whereclarity and long-term retention of an inert atmosphere are desired. Theblends may also be useful in bags for medical laundry, and forlamination of films to paper. The blends of the present invention may beused to form useful fibers. The blends may be processed from the melt orfrom a solvent-swollen gel. The melt-processable blends may be passedthrough an appropriate die to form filaments which may be stranded intosingle or multi-stranded fibers of various thicknesses. The fibers maythen be further processed into appropriate products, such as packagingmaterials, water-soluble disposable cloths, such as diapers, and thelike. The fibers may be post-treated after forming by chemicals whichwill insolubilize the poly(vinyl alcohol), and the resulting fibers maybe processed into articles with high moisture uptake which do notdissolve in water. Further, the polymers may be spun by a solid stateprocess wherein the fiber is oriented in the solid state to produce afiber with a very high tensile modulus.

Films from the present blends may be laminated, co-extruded, orco-injection molded to form laminated structures with a good combinationof clarity, toughness, and barrier properties. For example, a blend of a9:1 methyl methacrylate/methacrylic acid copolymer in admixture withpoly(vinyl alcohol) in a 50//50 mixture may be co-extruded withpoly(ethylene terephthalate) (PET), with poly(methyl methacrylate), withpoly(vinyl chloride), or with polycarbonate, to form continuouslaminated film with good adhesion between the layers. The co-extrudedfilm with PET can be thermoformed into useful objects withoutdelamination. The blend may be varied through other compositionalratios, such as 60//40 or 80//20, and other combinations of copolymer,poly(vinyl alcohol) and other polymer may be co-extruded usingtechnology known to the art. Multi-layer laminates may also be formed.

The blends described herein are also useful as hot-melt adhesives. Ahot-melt adhesive is a thermoplastic polymer that is heated to obtain aliquid of flowable viscosity, and after application in adhesive form, iscooled to obtain a solid which in the solid form has sufficient adhesiveand cohesive strength to maintain an acceptable adhesive bond againstthe test or use forces applied.

It is important with hot melt adhesives to join the two surfaces to bebonded together whilst the adhesive is still fluid. The term "open time"refers to the time interval between application of and setting orhardening of the molten adhesive. Hot melt additives are useful becausethey do not generate any water or solvent effluent, and thus areattractive for their lower cost, 100% efficiency, and their ecologicalbenefits.

Hot melt additives may be dispersed from small hand-made "guns" orvalved dispensing nozzles to large machines pumping adhesive throughslot jaws. They may also be dispersed in the foamed form. Forapplication of complex adhesive patterns, an embossed roll is used. Insome cases, the hot adhesive may be applied to one surface to be bonded,cooled, then re-heated at the time of bonding to the second surface. Insome cases, the adhesive may be in powder form; as such, it isdistributed upon one surface, heated in place, and the second surface tobe bonded then applied.

PVOH resins of diverse degree of hydrolysis and molecular weight arecurrently employed as adhesives in the fabrication of a large number ofproducts such as: bag making, carton sealing, Kraft paper band making,corrugating, paper tubing, book binding, paper board laminating,remoistenable adhesive (aqueous base), tapes, trading stamps, postagestamps, labels, decals, envelopes etc. The adhesive is prepared from aPVOH-water solution or suspension at a low (7-20% w/w) solid content.The substrate is coated with wax before application of the aqueoussolution. The adhesive coated substrate is dried at a temperaturegradient, which ranges from 80° to 170° C., in a drying oven for 10 to15 minutes. The above method of application of the adhesive is a directconsequence of the inherent thermal instability of PVOH. Because of thehigh cohesive energy density and polarity due to the hydroxy groups,attempts to melt PVOH result in severe degradation. The strong inter-and intramolecular interactions resulting from the high polarity of the--OH functional group give rise to a melting temperature in the vicinityof the degradation temperature of PVOH. Consequently, melting isaccompanied by degradation.

In order to render PVOH melt processable, steps have been taken to breakup the hydrogen bonding network and crystallinity by the addition ofexternal plasticizers. This technique is well known in the art andclearly elucidated in U.S. Pat. No. 3,143,518, which describes thepreparation and use of PVOH-propylene glycol compositions as hot meltadhesive. U.S. Pat. No. 3,121,701 also provides examples of the use ofhighly plasticized partially hydrolyzed PVOH as hot melt adhesive.Amongst the best known plasticizers of PVOH are the solid and liquidpolyols; these include polyethylene glycol, neopentyl glycol,2,2,4-trimethyl-1,3-pentanediol and glycerol respectively.

The use of small molecules or oligomers as plasticizers for hot meltadhesives based on PVOH has its inherent limitations and disadvantages.The current state of the art in PVOH hot melt adhesive technologyemploys 10-40 parts of plasticizer to 100 parts of PVOH. This high levelof plasticization leads to phase separation and embrittlement of theplasticized matrix. Low levels of plasticizer concentration, on theother hand, lead to the formation of highly viscous inextrudable meltsduring reprocessing. Upon re-melting plasticized PVOH, the low molecularweight plasticizer migrates and evaporates from the molten resin. In theabsence of the plasticizer, the PVOH rapidly recrystallizes andembrittles the adhesive. In the hot melt adhesive application, thisembrittlement compromises the integrity of the bond between adhesive andsubstrate. Another shortcoming of externally plasticized PVOH, whichmanifests itself when the plasticized PVOH resin comes into contact withalkaline or acidic solvents, is the hydrolysis and subsequentembrittlement of the partially hydrolyzed PVOH resin that is frequentlyused in the preparation of plasticized PVOH material.

One of the unexpected advantages of the use of the present acrylicadditives to plasticized PVOH is that the acrylic additive suppressesplasticizer migration. While it is desirable to use as little aspossible to achieve the desired end-use performance, for hot-meltadhesives, for example, it is possible (and indeed, preferred for thepurposes of lowering the viscosity of the melt at applicationtemperatures) to use up to 20 parts of plasticizer to decrease meltviscosity without undesirable plasticizer migration.

The examples described in TABLES XXII and XXIII are illustrative of theefficacy of the acrylic-modified PVOH as a hot melt adhesive. Thecomposition of each example is given in weight percent. The particularPVOH polymers used in the examples were obtained from AIR PRODUCTS(AIRVOL) and DuPont (ELVANOL). The polymers are as follows: AIRVOL-107is a fully hydrolyzed (98.0-98.8 mol %) resin having a solutionviscosity of 5.4-6.5 cPs determined on a 4% aqueous solution at 20° C.The molecular weight of this polymer is Mw=31-50,000. AIRVOL-321 is alsoa fully hydrolyzed PVOH resin of solution viscosity ranging from 16.5 to20.5 and Mw ranging from about 93 to 50,000. AIRVOL-205 is a partiallyhydrolyzed (87-89 mol %) resin of similar solution viscosity andmolecular weight to that of AIRVOL-107. ELVANOL-5105 is a low solutionviscosity (5-6 cPs), gel resistant, partially hydrolyzed (87-89 mol %)PVOH resin. The acrylic ter- and tetrapolymers were prepared fromcommercially available monomers (MMA, EA, NVP and MAA) by emulsionpolymerization and isolated by spray drying or coagulation.

The adhesive compositions may also include any or all of the following:preservatives, antioxidants, glyceryl ester of hydrogenated wood rosin,corn or potato starch, ethylene glycol, trimethylene glycol,tetramethylene glycol, pentamethylene glycol, hexamethylene glycol,propylene glycol, glycerin, 2,3-butanediol, 1,3-butanediol, diethyleneglycol, triethylene glycol, polyethylene glycol, ethyleneurea, urea,sorbitol and mannitol. A tackifying resin such as rosin or terpenephenol may also be added to the blend compositions. The use of lowlevels of glycerol is exemplified in the final examples.

In the hot-melt adhesive formulations, it may be desirable to havepresent in the second polymer, for purposes of improving adhesion of thehot melt to the cellulosic substrate, units of the structure ##STR40##wherein R₄ is H or C₁ -C₄ alkyl, and wherein R₈ is a urea or cyclicureido structure of the formula

EXAMPLES

This example teaches the general method for preparing copolymers ofmethyl methacrylate and methacrylic acid. A copolymer comprising 15weight percent methacrylic acid (MAA), and the remainder methylmethacrylate (MMA) was prepared by an emulsion polymerization techniqueas follows: A monomer mixture was prepared, which contained 1122 gramsof MMA, 198 grams of MAA, 10.56 grams of n-dodecyl mercaptan, 782.71grams of deionized water and 24.75 grams of a 10% aqueous sodiumdodecylbenzene sulfonate solution. To an appropriate glass vesselequipped with stirrer, heater, a reflux condenser, and nitrogen spargetube, was added 1753.26 grams of deionized water, and 0.59 grams ofsodium carbonate. The mixture was sparged for one hour with nitrogenwhile heating to 70° C. The sparge rate was then changed to a sweep and74.25 grams of a 10% aqueous solution of sodium dodecylbenzene sulfonatewas added to the mixture. The temperature of the reaction vessel wasthen raised to 85° C. At this temperature, 29.343 grams of the initiatormixture, which consisted of 1.32 grams of sodium persulfate and 380.08grams of deionized water, was added to the reaction vessel, along with31.42 mL of rinse water. The monomer mixture was then fed into thereaction vessel over a three-hour period.

As the polymerization proceeded, the initiator mixture was added to thereaction vessel at the rate of 29.34 mL every 15 minutes. Theaccumulation of solids was measured every 30 minutes just before theaddition of the initiator mixture. At the completion of the initiatorand monomer addition, followed by a 31.42 mL water rinse of each feedline, the mixture was held at 85° C. for one hour. The mixture was thencooled, filtered and the polymer isolated by freeze-drying. The polymerwas dried in a vacuum oven prior to blending experiments. The molecularweight of this polymer was about 80,000.

In a similar manner, other polymers of controlled molecular weight ofalkyl (meth)acrylates and unsaturated acids may be prepared.

The ASTM test methods employed are as follows: Specific Gravity-D792-66(re-approved 1979); Tensile-Yield, Elongation and Tensile ElasticModulus-D638-84; Tensile Impact Strength ASTM D1822; IzodImpact--D256-84; Charpy Impact ASTM D256; Heat Deflection TemperatureD648-72; Clash-Berg Torsional Modulus-D-1043; Oxygen Permeability ASTMD-3985.

The following solvent fractionation scheme was prepared to calculate thepercent of graft links and grafting efficiency of the (MMA-MAA) acryliccopolymers:

FLOW CHART: ##STR42##

The percent grafted PVOH and grafting efficiency of the acryliccopolymer (MMA-MAA), calculated from the above scheme and listed inTABLE IV, are supported qualitatively by FTIR spectra. The FTIR spectrashow increasing evidence of the presence of an ester carbonyl stretchingfrequency within the frequency range of 1726-1735 cm-1. It is noteworthyto mention that evidence of this ester is not discernible in either theFTIR spectrum of the acrylic terpolymer nor that of the poly(vinylalcohol). Hence, we may conclude that this ester functionality may haveresulted from the esterification reaction between the --OH of PVOH andthe --COOH of the acrylic polymer containing acid groups.

Another evidence of grafting is discernible from the increase intensile-modulus with increasing percent graft.

Example 1-58

These examples disclose typical blend conditions for blends reported inTable I.

PVOH and a copolymer of methyl methacrylate-methacrylic acid were dryblended in a polyethylene bag to form a mixture in a 80:20 % weightratio of PVOH to methyl methacrylate-co-MAA copolymer. For Airvol®205-based blends (Table I), the mixture was fed into the hopper of asingle screw Killion extruder in which the mixture was melt compoundedand extruded at the following extrusion conditions: extruder zone-1,180° C.; zone 2, 193° C.; zone 3, 193° C.; die-1 and die-2, 193° C.;screw speed 80 rpm. The pelletized samples were dried in a forced airoven and then molded in an Arburg injection molding machine equippedwith a heated ASTM family mold for the formation of test pieces. Themolding conditions were: nozzle: 199° C.; zones 1, 2, and 3: 200° C.;injection pressure 6.2 MPa; back pressure 1.4 MPa; mold temperature 24°C.

For Airvol® 107-based blends (Table I), the mixture was fed into thehopper of a single screw Killion extruder in which the mixture was meltcompounded and extruded at the following extrusion conditions: extruderzone-1, 199° C.; zone 2, 216° C.; zone 3, 216° C.; die-1 and die-2, 210°C.; screw speed 80 rpm. The pelletized samples were dried in a forcedair oven and then molded in an Arburg injection molding machine equippedwith a heated ASTM family mold for the formation of test pieces. Themolding conditions were: nozzle: 226° C.; zones 1, 2, and 3: 235°-240°C.; injection pressure 6.6 MPa; back pressure 1.4 MPa; mold temperature35° C.

Other conditions may be used, depending on the viscosity of the blend.Tg, and crystallinity (% Crys.) are measured by differential scanningcalorimetry.

Tables II and III summarize the physical properties of the blends. TableIV describes the extent of grafting in one blend thoroughly analyzed.

The following table identifies starting materials and blends for whichdata are presented in the subsequent tables.

                                      TABLE 1                                     __________________________________________________________________________    Thermal Properties of Homopolymers and Blends                                 107(PVOHystems: P(MMA-MAA)/Airvol ®                                       205(87-89% hydrolyzed PVOH/VAc, Mw ®                                      31-50,000                                                                                           Comp.     Tg  Tm  Crys.                                 No.                                                                              Polymer Blend      % w/w                                                                              Mw   (°C.)                                                                      (°C.)                                                                      (%)                                   __________________________________________________________________________    107Airvol ®       100  31-50 k                                                                            75.29                                                                             221.58                                                                            47.57                                 2. P(MMA-MAA = 99/01) 100  168 k                                                                              124.24                                        3. P(MMA-MAA = 97/03) 100  182 k                                                                              127.69                                        4. P(MMA-MAA = 95/05) 100  152 k                                                                              129.10                                        5. P(MMA-MAA = 93/07) 100  172 k                                                                              136.71                                        6. P(MMA-MAA = 90/10) 100  179 k                                                                              142.29                                        7. P(MMA-MAA = 85/15) 100  179 k                                                                              151.24                                        8. P(MMA-MAA = 80/20) 100  199 k                                                                              159.60                                        107/P(MMA-MAA = 99/01)                                                           80/20              (Ex. 2)                                                                            74.28                                                                              217.67                                                                            39.46                                     10.                                                                           107/P(MMA-MAA = 97/03)                                                           80/20              (Ex. 3)                                                                            73.46                                                                              218.33                                                                            40.04                                     107/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 4)                                                                            73.71                                                                              218.88                                                                            36.27                                     107/P(MMA-MAA = 93/07)                                                           80/20              (Ex. 5)                                                                            75.08                                                                              219.78                                                                            39.45                                     107/P(MMA-MAA = 80/20)                                                           80/20              (Ex. 6)                                                                            75.30                                                                              219.94                                                                            39.72                                     107/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 7)                                                                            75.30                                                                              221.20                                                                            43.89                                     107/P(MMA-MAA = 80/20)                                                           80/20              (Ex. 8)                                                                            74.59                                                                              220.60                                                                            40.73                                     205Airvol ®       31-50 k                                                                            68.26                                                                              173.42                                                                            13.75                                     205/P(MMA-MAA = 99/01)                                                           80/20              (Ex. 2)                                                                            69.69                                                                              185.21                                                                            21.43                                     205/P(MMA-MAA = 97/03)                                                           80/20              (Ex. 3)                                                                            69.22                                                                              188.06                                                                            22.67                                     205/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 4)                                                                            69.64                                                                              190.85                                                                            22.78                                     20.                                                                           205/P(MMA-MAA = 93/07)                                                           80/20              (Ex. 5)                                                                            69.18                                                                              193.06                                                                            26.17                                     205/P(MMA-MAA = 90/10)                                                           80/20              (Ex. 6)                                                                            70.24                                                                              191.37                                                                            24.81                                     205/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 7)                                                                            69.93                                                                              192.58                                                                            24.23                                        P(MMA-MAA = 95/05) 100  126 k                                                                              129.90                                           P(MMA-MAA = 95/05) 100  78.6 k                                                                             125.90                                           P(MMA-MAA = 95/05) 100  66.4 k                                                                             126.10                                           P(MMA-MAA = 95/05) 100  37.1 k                                                                             120.00                                           P(MMA-MAA = 90/10) 100  122.0 k                                                                            138.10                                           P(MMA-MAA = 90/10) 100  78.9 k                                                                             136.50                                           P(MMA-MAA = 90/10) 100  63.1 k                                                                             134.20                                        30.                                                                              P(MMA-MAA = 90/10) 100  42.3 k                                                                             130.70                                           P(MMA-MAA = 85/15) 100  80.1 k                                                                             149.30                                           P(MMA-MAA =  85/15)                                                                              100  76.0 k                                                                             148.00                                           P(MMA-MAA = 85/15) 100  60.6 k                                                                             143.60                                           P(MMA-MAA = 85/15) 100  39.3 k                                                                             139.10                                        205/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 23)                                                                           69.92                                                                              180.18                                                                            19.62                                     205/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 24)                                                                           70.99                                                                              177.31                                                                            20.18                                     205/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 25)                                                                           71.02                                                                              183.81                                                                            19.72                                     205/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 26)                                                                           72.03                                                                              183.37                                                                            18.57                                     205/P(MMA-MAA = 90/10)                                                           80/20              (Ex. 27)                                                                           69.79                                                                              189.86                                                                            22.84                                     40.                                                                           205/P(MMA-MAA = 90/10)                                                           80/20              (Ex. 28)                                                                           70.70                                                                              188.93                                                                            24.61                                     205/P(MMA-MAA = 90/10)                                                           80/20              (Ex. 29)                                                                           70.81                                                                              189.24                                                                            22.45                                     205/P(MMA-MAA = 90/10)                                                           80/20              (Ex. 30)                                                                           71.52                                                                              187.70                                                                            22.38                                     205/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 31)                                                                           70.72                                                                              192.00                                                                            23.80                                     205/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 32)                                                                           70.63                                                                              190.88                                                                            23.79                                     205/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 33)                                                                           71.25                                                                              191.66                                                                            24.14                                     205/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 34)                                                                           71.88                                                                              192.04                                                                            24.13                                     107/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 23)                                                                           75.96                                                                              225.02                                                                            48.16                                     107/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 24)                                                                           75.28                                                                              222.77                                                                            48.50                                     107/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 25)                                                                           75.96                                                                              222.50                                                                            47.55                                     50.                                                                           107/P(MMA-MAA = 95/05)                                                           80/20              (Ex. 26)                                                                           75.71                                                                              222.94                                                                            46.34                                     107/P(MMA-MAA = 90/10)                                                           80/20              (Ex. 27)                                                                           78.24                                                                              223.99                                                                            49.94                                     107/P(MMA-MAA = 90/10)                                                           80/20              (Ex. 28)                                                                           77.10                                                                              223.65                                                                            47.22                                     107/P(MMA-MAA = 90/10)                                                           80/20              (Ex. 29)                                                                           76.08                                                                              222.98                                                                            47.12                                     107/P(MMA-MAA = 90/10)                                                           80/20              (Ex. 30)                                                                           80.85                                                                              223.47                                                                            44.67                                     107/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 31)                                                                           77.92                                                                              224.30                                                                            48.38                                     lO7/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 32)                                                                           76.91                                                                              224.52                                                                            45.93                                     107/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 33)                                                                           77.98                                                                              223.85                                                                            46.85                                     107/P(MMA-MAA = 85/15)                                                           80/20              (Ex. 34)                                                                           76.61                                                                              224.26                                                                            46.37                                     __________________________________________________________________________

The data in Table I indicates that for the PVOH homopolymer, theaddition of the additive polymers only slightly lowers the crystallinemelting point, and only slightly decreases the glass temperature, whilea lowered, but still high degree of crystallinity is maintained. For thePVOH/PVAc copolymer, the addition of the additive polymers raises thecrystalline melting point and the glass temperature, while the degree ofcrystallinity is enhanced.

                  TABLE II                                                        ______________________________________                                        Physical Properties of Alloys with PVOH Homopolymer:                          Variations in MAA Content of Modifier                                         ______________________________________                                                   Examples                                                           Physical Properties                                                                        10      12      13    14    15                                   ______________________________________                                        Specific Gravity     1.28    1.28  1.28  1.29                                 Tensile-Yield, mPa   127     129   --    131                                  Elongation @ 4.16    12.66   10.78 3.52  4.44                                 Break %                                                                       Tensile-Modulus, mPa                                                                       3458    5925    5967  5884  5870                                 Tensile Impact                                                                             36575   96692   82819 63691 57595                                Strength (Joules/M.sup.2)                                                     Dynatup Impact                                                                             1.50    1.93    1.71  1.60  1.31                                 Strength (Joules)                                                             Notched Izod @ 0° C.                                                                        20.82   22.42 23.49 24.55                                (Joules/M)                                                                    Notched Izod @                                                                             21.35   23.49   22.95 21.35 21.35                                23° C. (Joules/M)                                                      Unnotched Izod @                                                                           530     414     496   385   367                                  23° C. (Joules/M)                                                      Unnotched Charpy                                                                           112919  96019   95515 88494 79918                                (Joules/0.5 M.sup.2) @                                                        23° C.                                                                 DTUFL (264 kPa,                                                                            582     574     570   630   671                                  2° C./min.) (un-                                                       annealed) °C.                                                          DTUFL (264 kPa,                                                                            633     640     660   656   647                                  2° C./min) (ann.                                                       4 hrs. @ 80° C.), °C.                                           Clash-Berg Torsional                                                          Modulus,                                                                      mPa @ 40° C.  5094    5094  5377  4993                                 mPa @ 80° C.  1169    955   936   1311                                 mPa @ 120° C. 330     297   312   397                                  ______________________________________                                                       Examples                                                       Physical Properties                                                                            47      50      54    58                                     ______________________________________                                        Elongation @ Break %                                                                           116.95  2.94    3.62  3.62                                   Tensile-Modulus, mPa                                                                           5874    6009    6173  6102                                   Tensile ImPact Strength                                                                        70837   46034   54442 42460                                  (Joules/M.sup.2)                                                              Dynatup ImPact Strength                                                                        1.76    2.08    1.88  2.01                                   (Joules)                                                                      Notched Izod @ 0° C.                                                                    20.82   13.88   16.55 15.48                                  (Joules/M)                                                                    Notched Izod @ 23° C.                                                                   22.95   14.41   15.48 14.41                                  (Joules/M)                                                                    Unnotched Charpy 77816   53559   4666  41872                                  (Joules/0.5 M.sup.2) @ 23° C.                                          DTUFL (264 kPa, 2° C./min.)                                                             600     594     593   634                                    (unannealed) °C.                                                       Clash-Berg Torsional Modulus,                                                 mPa @ 40° C.      5426    5610  5240                                   mPa @ 80° C.      1221    1122  1135                                   mPa @ 120° C.     326     421   401                                    ______________________________________                                    

In the following table are summarized the properties of the blends withthe partially hydrolyzed PVOH (Airvol®-205) with several of the additivecopolymers of poly(methyl methacrylate-methacrylic acid). In general,tensile modulus is improved with increasing the amount of acid suppliedby the copolymer in the blend, while tensile impact strength isdecreased.

                                      TABLE III                                   __________________________________________________________________________    Physical Properties of Alloys with Partially-Hydrolyzed PVOH: Variations      in                                                                            MAA Content and Molecular Weight of Modifier                                  __________________________________________________________________________                   Examples                                                       Physical Properties                                                                          17  18  19  20  21  22  35  36  37  38                         __________________________________________________________________________    Specific Gravity                                                                             1.26                                                                              1.26                                                                              1.26                                                                              1.26                                                                              1.26                                                                              1.26                                                                              1.26                                                                              1.26                                                                              1.26                                                                              1.26                       Tensile Yield, mPa                                                                           85.64                                                                             82.82                                                                             82.68                                                                             82.89                                                                             82.20                                                                             81.99                                                                             95.22                                                                             95.22                                                                             97.15                                                                             99.84                      Elongation @ Break %                                                                         60.40                                                                             28.80                                                                             75.20                                                                             62.10                                                                             61.90                                                                             59.50                                                                             68.70                                                                             94.50                                                                             63.10                                                                             44.70                      Tensile-Modulus, mPa                                                                         4719                                                                              4445                                                                              4620                                                                              4755                                                                              4781                                                                              4837                                                                              5540                                                                              5312                                                                              5602                                                                              5815                       Tensile Impact Strength                                                                      90596                                                                             87674                                                                             84711                                                                             77774                                                                             38856                                                                             60327                                                                             124228                                                                            83239                                                                             74831                                                                             46664                      (Joules/M.sup.2)                                                              Dynatup Impact Strength                                                                      4.12                                                                              3.41                                                                              3.16                                                                              2.60                                                                              2.79                                                                              2.31                                                                              2.26                                                                              1.80                                                                              2.20                                                                              1.01                       (Joules)                                                                      Notched Izod @ 0° C.                                                                  17.62                                                                             17.08                                                                             19.75                                                                             21.89                                                                             22.95                                                                             22.42                                                                             23.49                                                                             20.28                                                                             12.81                                                                             13.35                      (Joules/M)                                                                    Notched Izod @ 23° C.                                                                 22.95                                                                             24.02                                                                             21.89                                                                             21.89                                                                             21.35                                                                             16.01                                                                             19.75                                                                             11.21                                                                             11.74                                                                             14.41                      (Joules/M)                                                                    Unnotched Izod @ 23° C.                                                               378 360 492 358 354 349 637 558 399 135                        (Joules/M)                                                                    Unnotched Charpy                                                                             80759                                                                             73192                                                                             80338                                                                             79582                                                                             67979                                                                             70249                                                                             87191                                                                             99214                                                                             46307                                                                             70837                      (Joules/0.5 M.sup.2) @ 23° C.                                          DTUFL (264 kPa, 2° C./min.)                                                           433 459 443 463 444 446 461 452 464 452                        (unannealed) °C.                                                       DTUFL (264 kPa, 2° C./min.)                                                           469 452 464 450 461 449 473 463 486 470                        (ann. 4 hrs. @ 80° C.), °C.                                     Clash-Berg Torsional Modulus,                                                 mPa @ 40° C.                                                                          3617                                                                              3185                                                                              3204                                                                              3270                                                                              3996                                                                              3872                                                                              3764                                                                              3597                                                                              3850                                                                              3587                       mPa @ 80° C.                                                                          217 171 181 200 200 235 194 195 205 166                        mPa @ 120° C.                                                                         55  58  61  67  69  77  56  37  35  29                         __________________________________________________________________________                           Examples                                                       Physical Properties                                                                          39  40  41  42  43  44  45  46                         __________________________________________________________________________            Specific Gravity                                                                             1.26                                                                              1.26                                                                              1.26                                                                              1.26                                                                              1.26                                                                              1.27                                                                              1.26                                                                              1.26                               Tensile Yield, mPa                                                                           94.39                                                                             94.46                                                                             95.36                                                                             99.15                                                                             95.56                                                                             95.56                                                                             94.94                                                                             96.12                              Elongation @ Break %                                                                         68.7                                                                              79.4                                                                              58.5                                                                              33.9                                                                              72.30                                                                             92.40                                                                             69.90                                                                             60.20                              Tensile-Modulus, mPa                                                                         5388                                                                              5409                                                                              5519                                                                              5753                                                                              5340                                                                              5409                                                                              5422                                                                              5519                               Tensile Impact Strength                                                                      68105                                                                             151344                                                                            152185                                                                            31740                                                                             73780                                                                             86813                                                                             130955                                                                            86392                              (Joules/M.sup.2)                                                              Dynatup Impact Strength                                                                      3.70                                                                              2.82                                                                              1.75                                                                              1.12                                                                              1.86                                                                              1.47                                                                              1.59                                                                              1.20                               (Joules)                                                                      Notched Izod @ 0° C.                                                                  18.15                                                                             14.41                                                                             14.41                                                                             13.35                                                                             20.82                                                                             20.82                                                                             13.35                                                                             17.62                              (Joules/M)                                                                    Notched Izod @ 23° C.                                                                 16.55                                                                             13.35                                                                             10.68                                                                             13.88                                                                             17.08                                                                             19.75                                                                             12.28                                                                             16.01                              (Joules/M)                                                                    Unnotched Izod @ 23° C.                                                               420 469 515 106 429 501 562 357                                (Joules/M)                                                                    Unnotched Charpy                                                                             95683                                                                             95977                                                                             96440                                                                             49313                                                                             90554                                                                             88242                                                                             84542                                                                             72309                              (Joules/0.5 M.sup.2) @ 23° C.                                          DTUFL (264 kPa, 2° C./min.)                                                           460 455 464 459 451 446 464 447                                (unannealed) °C.                                                       DTUFL (264 kPa, 2° C./min.)                                                           467 471 484 484 476 461 476 467                                (ann. 4 hrs. @ 80° C.), °C.                                     Clash-Berg Torsional Modulus,                                                 mPa @ 40° C.                                                                          3872                                                                              3645                                                                              3574                                                                              3496                                                                              3872                                                                              3645                                                                              3573                                                                              3496                               mPa @ 80° C.                                                                          242 208 223 235 242 208 223 235                                mPa @ 120° C.                                                                         68  60  66  69  68  60  66  69                         __________________________________________________________________________

                  TABLE IV                                                        ______________________________________                                        107FTING OF P(MMA-MAA) ONTO Airvol ®                                             Initial Wt.                                                                             Wt. of PVOH Percent Graft                                           of PVOH   After Grafting                                                                            Graft   Efficiency                               Example                                                                              (g)       (g)         (%)     (%)                                      ______________________________________                                        13     2.4093    2.6927      11.76   61.30                                    14     2.4048    2.7312      13.57   49.00                                    ______________________________________                                    

Example 59

In the specific examples which follow presenting blend data, thefollowing poly(vinyl alcohol) polymers and processing conditions areused.

The particular PVOH materials used in the Examples were obtained fromAir Products. They are as follows: Airvol-107, is a fully hydrolyzed(98.0-98.8 mol %) resin having a solution viscosity of 5.4-6.5 cPsdetermined on a 4% aqueous solution at 20° C. The Mw of this PVOH is31,000-50,000. Another PVOH resin employed is Air Products Airvol-205which is a partially hydrolyzed (87-89 mol %) resin possessing asolution viscosity of 5-6 cPs when determined on a 4% aqueous solutionat 20° C. Airvol-205 has Mw of 31,000-50,000. Two other PVOH polymersreferred to are Airvol-103 and Airvol-325. Airvol-103 is a fullyhydrolyzed (98.0-98.8 MOL %) resin having a solution viscosity of3.2-4.2 cPs(Mw=13-23k) determined on a 4% aqueous solution at 20° C.Airvol-325 is also a fully hydrolyzed PVOH resin, Mw=85-146k.

The PVOH (Airvol-205) specified above and the acrylic or styreniccopolymers were dry blended in a polyethylene bag to yield wellhomogenized mixtures. The mixtures were fed into the hopper of a singlescrew Killion extruder in which the mixtures were melt compounded andextruded at the following extrusion conditions:

    ______________________________________                                        EXTRUDER BARREL TEMPERATURES:                                                                         ZONE-1:  180° C.                                                       ZONE-2:  193° C.                                                       ZONE-3:  193° C.                               DIE TEMPERATURES:       DIE-1:   193° C.                                                       DIE-2:   193° C.                               SCREW SPEED:            80 RPM                                                ______________________________________                                    

The mechanical properties of the alloy were evaluated with the aid ofparts which were prepared by injection molding by the followingprocedure:

The pelletized extrudates were dried in a forced air oven prior toinjection molding in an Arburg injection molding machine equipped with aheated ASTM family mold. The molding conditions were as follows:

    ______________________________________                                        INJECTION MOLDER     NOZZLE:   199° C.                                 TEMPERATURES:        ZONE-1:   200° C.                                                      ZONE-2:   200° C.                                                      ZONE-3:   200° C.                                 INJECTION PRESSURE:  6.2 MPa                                                  BACK PRESSURE:       1.4 MPa                                                  MOLD TEMPERATURE:    24° C.                                            ______________________________________                                    

The PVOH (Airvol-107) specified above and the acrylic or styreniccopolymers were dry blended to yield homogeneous mixtures. The mixtureswere fed into the hopper of a single screw Killion Extruder where thedry powder was melt compounded, extruded and pelletized at temperaturesranging from 199°-216° C. and screw speed of 80 RPM.

    ______________________________________                                        EXTRUDER BARREL TEMPERATURES:                                                                         ZONE-1:  199° C.                                                       ZONE-2:  216° C.                                                       ZONE-3:  216° C.                               DIE TEMPERATURES:       DIE-1:   210° C.                                                       DIE-2:   210° C.                               SCREW SPEED:            80 RPM                                                ______________________________________                                    

The mechanical properties of the alloy were evaluated with the aid ofparts which were prepared by injection molding by the followingprocedure:

The pelletized extrudates were dried in a forced air oven prior toinjection molding in an Arburg injection molding machine equipped with aheated ASTM family mold. The molding conditions were as follows:

    ______________________________________                                        INJECTION MOLDER     NOZZLE:   226° C.                                 TEMPERATURES:        ZONE-1:   235° C.                                                      ZONE-2:   240° C.                                                      ZONE-3:   240° C.                                 INJECTION PRESSURE:  6.6 MPa                                                  BACK PRESSURE:       1.4 MPa                                                  MOLD TEMPERATURE:    35° C.                                            ______________________________________                                    

When processed by themselves, the Airvol-107, -205, and -325 produced ayellow, unstable melt, and were unsuitable for melt-processing. Airvol103 was not tested by itself in this series.

Examples 60-70

The following examples illustrate thermal and physical properties ofblends with specific poly(vinyl alcohol) polymers of a polymer of methylmethacrylate containing glutaric anhydride (MMA-GAH) units or with astyrene/maleic anhydride (St-MAH) copolymer. The latter polymer is soldcommercially as Dylark® 232, and is believed to contain ca. 8 mol % ofunits derived from maleic anhydride. The former polymer is prepared bythe method of Hallden-Abberton et al., U.S. Pat. No. 4,874,824 from apoly(methyl methacrylate) homopolymer of MW ca. 150,000.

                                      TABLE V                                     __________________________________________________________________________    Thermal Properties of Acrylic and Styrenic Copolymers                         containing Anhydride Groups and Blends of the same with Airvol-107 and        Airvol-205 Vinyl                                                              Alcohol Polymers                                                                                    COMP.                                                   EX.                                                                              POLYMER/BLEND      % w/w                                                                              Mw Tg (°C.)                                                                     Tm (°C.)                                                                    CRYS. (%)                            __________________________________________________________________________    60.                                                                              P(ST-MAH = 92/08)  100  270 k                                                                            122.8                                              P(MMA-GAH = 91.4/8.6)                                                                            100  150 k                                                                            121.3                                              Airvol-107/P(ST-MAH = 92/8)                                                                      80/20   116.7;76.4                                                                          225.2                                                                              39.7                                    Airvol-205/P(ST-MAH = 92/8)                                                                      80/20   110.8;68.4                                                                          186.4                                                                              16.2                                    Airvol-107/P(MMA-GAH = 91.4/8.6)                                                                 80/20   74.5  223.5                                                                              36.3                                 __________________________________________________________________________

                  TABLE VI                                                        ______________________________________                                        Physical Properties of Alloys Consisting of Airvol-205 and the                Acrylic and Styrenic Copolymers: P(MMA-GAH)                                   and P(Styrene-co-Maleic Anhydride).                                                              Examples                                                                      65   64     66     67                                      ______________________________________                                        POLYMER                                                                       Airvol-205           90     80     70   90                                    P(MMA-GAH = 91.4/8.6)                                                                              10     20     30                                         P(ST-MAH = 92/8)                        10                                    PHYSICAL PROPERTIES                                                           TENSILE-YIELD, MPa   96.9   93.0   89.4 95.2                                  ELONGATION @ BREAK % 66.0   53.5   61.3 92.4                                  TENSILE-MODULUS, GPa 5.4    5.2    4.9  5.5                                   DYNATUP IMPACT       2.2    2.4    1.3  3.6                                   STRENGTH, J                                                                   NOTCHED IZOD @ 23° C. J/m                                                                   24.0   23.5   23.5 28.8                                  UNNOTCHED IZOD @ 23° C. J/m                                                                 577.0  489.0  407.0                                                                              828.0                                 DTUFL (1.8 MPa, 2° C./min.)                                                                 63.8   65.4   64.8 65.0                                  (unannealed) °C.                                                       DTUFL (1.8 mPa, 2° C./min.)                                                                 64.7   66.9   65.8 66.1                                  (ann. 4 hrs. @ 80° C.), °C.                                     ______________________________________                                    

                  TABLE VII                                                       ______________________________________                                        Physical Properties of Alloys Consisting of Airvol-107,                       Airvol-205 and the Acrylic and Styrenic Copolymers:                           P(MMA-GAH) and P(ST-MAH).                                                                        Examples                                                                      68   69     64     70                                      ______________________________________                                        POLYMERS                                                                      Airvol-107           90     90     80   70                                    P(MMA-GAH = 91.4/8.6)                                                                              10            20   30                                    P(ST-MAH = 92/8)            10                                                PHYSICAL PROPERTIES                                                           TENSILE-YIELD, MPa   132.0  127.0  130.0                                                                              127.0                                 ELONGATION @ BREAK % 3.4    4.6    10.1 10.6                                  TENSILE-MODULUS, GPa 6.6    6.8    6.9  6.9                                   DYNATUP IMPACT       1.9    2.9    2.0  2.5                                   STRENGTH, J                                                                   NOTCHED IZOD @ 23° C. J/m                                                                   24.0   25.6   21.4 22.4                                  UNNOTCHED IZOD @ 23° C. J/m                                                                 339.0  452.0  555.0                                                                              512.0                                 DTUFL (1.8 MPa, 2° C./min.)                                                                 86.6   89.2   91.5 94.8                                  (unannealed) °C.                                                       DTUFL (1.8 MPa, 2° C./min.)                                                                 90.9   92.2   96.4 96.0                                  (ann. 4 hrs. @ 80° C.), °C.                                     ______________________________________                                    

Examples 70-81

These examples demonstrate that grafts of styrene polymers containingacid groups when grafted to a polyolefin trunk are ineffective inmodifying the poly(vinyl alcohol) to improve its melt processing, as aredirect grafts of acrylic acid to a polyolefin trunk.

The styrene/(meth)acrylic graft copolymers were prepared bypolymerization of the appropriate monomer mixture in the presence ofpreformed polypropylene, mfr=4 in the absence of solvent, swelling ofthe polypropylene being conducted prior to initiation. The graft ofMMA/N-VP (N-vinylpyrrolidone) was prepared in a similar manner.

The thermal properties of blends in the system graft polymer(polypropylene/styrene/(meth)acrylic acid)//PVOH were investigated bymelt mixing in a single screw Killion extruder. The homopolymers andalloys listed in Table VII were extruded and pelletized at temperaturesranging from 180° to 200° C. for partially hydrolyzed PVOH (Airvol-205)and 200° to 216° C. for fully hydrolyzed PVOH (Airvol-107 andAirvol-325). All compositions, listed in Table VII, are given in weightpercent. Examples C₁ -C₃ are controls of the unmodifiedpoly(vinylalcohols). As can be seen from the data listed in Table VII,the melt compounding of the graft terpolymers with the severalpoly(vinyl alcohol)s resulted in alloys which exhibited varying degreesof melt instability. The term `UNSTABLE MELT` (Table VII) refers to theappearance of the melted PVOH or PVOH/graft terpolymer blends. `UnstableMelt` indicates a combination of degradation, phase separation and crosslinking during the melt compounding and extrusion processes. The thermalstability of the alloys, in the molten state, may qualitatively bedetermined from the surface texture of the extrudates. The extrudatesderived from the compositions listed in Table VII range in color frompale yellow to yellowish white. The former color was observed for thosecompositions in which the weight percent of -MAA or AA in the graftterpolymer was less than five weight percent. Particularly, it should benoted that the absence of acid and or anhydride in the graft terpolymer,PP-g-MMA-NVP, EX. 70 of Table VII, may have contributed to the blendbeing of a darker hue than those blends which contain acidfunctionalized polypropylene graft copolymers. It was observed that allof the alloys exhibited significant amounts of melt fracture. Theinhomogeneous nature of the melt was also reflected in the form of lowmelt viscosity which led to decrease in the extruder torque during meltprocessing. This decrease, in torque, may be attributed to poor mixingbetween the blend components. Similar observations, shown in Table VIII,were encountered when the graft copolymer (polypropylene-g-acrylic acid)(PP-g-AA) was melt compounded with PVOH (Airvol-107 and Airvol-325). Thegraft copolymers are a commercial product; the exact nature of the trunkpolymer or of the length of the acrylic acid grafted chains is notknown.

                                      TABLE VIII                                  __________________________________________________________________________    Thermal Properties of Polymer Blends in the System: Graft Terpolymer          (PP-                                                                          g-ST-MAA and PP-g-ST-AA)/Airvol-107.                                                             COMP.          THERMAL                                     EX.                                                                              POLYMER/BLEND   % (W/W)                                                                             COLOR    STABILITY                                   __________________________________________________________________________    C1.                                                                              Airvol-107      100   YELLOW   UNSTABLE MELT                               C2.                                                                              Airvol-325      100   YELLOW   UNSTABLE MELT                               C3.                                                                              Airvol-205      100   YELLOW   UNSTABLE MELT                               70.                                                                              Airvol-107/(PP-g-MMA-NVP =                                                                    80/20 YELLOW   UNSTABLE MELT                                  ca. 80/19/1                                                                   Airvol-107/(PP-g-ST-AA =                                                                      80/20 PALE YELLOW                                                                            UNSTABLE MELT                                  79.5/13.6/6.8)                                                                Airvol-107/(PP-g-ST-AA =                                                                      80/20 PALE YELLOW                                                                            UNSTABLE MELT                                  81.4/14.0/4.6)                                                                Airvol-107/(PP-g-ST-MAA =                                                                     80/20 PALE YELLOW                                                                            UNSTABLE MELT                                  81.4/14.0/4.6)                                                             __________________________________________________________________________

                                      TABLE IX                                    __________________________________________________________________________    Thermal Properties of Blends in the System: Graft Copolymer (PP-g-            AA)/Airvol-107 and Airvol-325.                                                               COMP.          THERMAL                                         EX.                                                                              POLYMER/BLEND                                                                             % (W/W)                                                                             COLOR    STABILITY                                       __________________________________________________________________________       Airvol-107/(PP-g-AA =                                                                     80/20 PALE YELLOW                                                                            UNSTABLE MELT                                      98/02, Mfr = 12 dg/min.)                                                      Airvol-107/(PP-g-AA =                                                                     80/20 PALE YELLOW                                                                            UNSTABLE MELT                                      94/06, Mfr = 20 dg/min.)                                                      Airvol-107/(PP-g- =                                                                       80/20 PALE YELLOW                                                                            UNSTABLE MELT                                      98/02, Mfr = 20 dg/min.)                                                      Airvol-107/(PP-g-AA =                                                                     80/20 PALE YELLOW                                                                            UNSTABLE MELT                                      98/02, Mfr = 40 dg/min.)                                                      Airvol-325/(PP-g-AA =                                                                     80/20 PALE YELLOW                                                                            UNSTABLE MELT                                      98/02, Mfr = 12 dg/min.)                                                      Airvol-325/(PP-g-AA =                                                                     80/20 YELLOW   UNSTABLE MELT                                      94/06, Mfr = 20 dg/min.)                                                   80.                                                                              Airvol-325/(PP-g-AA =                                                                     80/20 PALE YELLOW                                                                            UNSTABLE MELT                                      98/02, Mfr = 20 dg/min.)                                                      Airvol-325/(PP-g-AA =                                                                     80/20 PALE YELLOW                                                                            UNSTABLE MELT                                      98/02, Mfr = 40 dg/min.)                                                   __________________________________________________________________________

Examples 82-90

These examples illustrate the utility of a multistage polymer with abutyl acrylate/acrylic acid first stage and a styrene or astyrene/methyl methacrylate second stage in improving the meltprocessability of poly(vinyl alcohol).

The composition delineated by Ex. 85, Table IX, represents a ternaryblend comprising of a medium molecular weight (Mw=85-146k) PVOH(Airvol-325), the impact modifier of Example 82, and the acrylicterpolymer, P(MMA-NVP-MAA=73/25/02). The impact modifier of Example 82is a multistage polymer prepared by first emulsion polymerizing butylacrylate/ethyl acrylate/methacrylic acid (60/16/4) and then polymerizingstyrene/divinylbenzene (9/1) and then styrene (10) with a low level ofdodecyl mercaptan. The polymer is isolated by coagulation from emulsion.The preparation of the acrylic terpolymer in emulsion is by a processvery similar to that described in Example 1.

This alloy, in addition to being `melt stable`, was found to exhibit agreater degree of toughness than a similarly prepared alloy in which theimpact modifier of Example 82 is absent. The thermal properties of thealloy, Tg, Tm and percent crystallinity are comparable to that of thematrix polymer, Airvol-325. This suggests that the combined effect ofthe impact modifier and P(MMA-NVP-MAA=73/25/02) is the improvement ofthe mechanical properties of the PVOH alloy without significantlyaltering the thermodynamic properties of the PVOH.

                                      TABLE X                                     __________________________________________________________________________    Thermal Properties of Homopolymers and Blends in the                          System Ex. 82/Airvol-107, Airvol-205 and Airvol-325.                                                       Tg (°C.)                                  EX.                                                                              POLYMER/BLEND   COMP.                                                                              Mw   % w/w                                                                              Tm (°C.)                                                                    CRYS. (%)                              __________________________________________________________________________    C1.                                                                              Airvol-107      100  31-50 k                                                                            75.29                                                                              221.58                                                                             47.57                                  C2.                                                                              Airvol-325      100  85-146 k                                                                           77.55                                                                              225.77                                                                             44.23                                  C3.                                                                              Airvol-205      100  31-50 k                                                                            69.29                                                                              167.11                                                                             23.77                                     Impact Modifier 100                                                           Airvol-107/Ex. 82                                                                             80/20     72.93                                                                              222.36                                                                             42.45                                     Airvol-205/Ex. 82                                                                             80/20     67.94                                                                              193.63                                                                             22.22                                     Airvol-325/Ex. 82/                                                                            80/4/16   76.56                                                                              225.94                                                                             40.39                                     P(MMA-NVP-MAA = 73/25/2                                                    __________________________________________________________________________

Impact modifier Example 86 is somewhat similar to the impact modifier ofExample 82. It is prepared by first polymerizing 80 parts of butylacrylate/ethyl acrylate/diallyl maleate/butylene glycoldiacrylate/methacrylic acid (74.5/20/0.4/0.1/5.0) then polymerizing 20parts of methyl methacrylate/styrene/divinylbenzene/butylene glycoldiacrylate (69/30/0.7/0.3), and isolating by coagulation.

The mechanical properties of binary and ternary blends in the system:PVOH/P(MMA-NVP-MAA)/Ex. 86 are presented in TABLE X. It should be notedfrom a comparison of Examples 87 and 88 in Table X that theincorporation of the impact modifier of Example 86 into the binary blendof Airvol-107 and P(MMA-NVP-MAA) terpolymer leads to an improvement inthe tensile yield strength of the final blend composition. Slightimprovement is also seen in the impact property of the blend. The blenddesignated as Ex. 89 also shows marginal improvement in mechanicalproperties over that measured for blends without the impact modifier ofExample 86. The blend of the low molecular weight (Mw=13-23k) fullyhydrolyzed PVOH (Airvol-103) with the impact modifier of Example 86,surprisingly exhibited poor overall mechanical properties.

                  TABLE XI                                                        ______________________________________                                        Physical Properties of Ternary Blends in the Systems Airvol-107,              Airvol-205 and Acrylic Terpolymers: P(MMA-NVP-MAA).                                           Examples                                                                      87    88      89      90                                      ______________________________________                                        POLYMERS                                                                      Airvol-107        85      78.7                                                Airvol-103                              85                                    Airvol-205                        78.7                                        P(MMA-NVP-MAA = 70/25/5)                                                                        15      13.8                                                P(MMA-NVP-MAA = 73/25/2)          13.8                                        EXAMPLE 86                7.4     7.4   15                                    PHYSICAL PROPERTY                                                             SPECIFIC GRAVITY  1.29    1.27    1.25  1.24                                  TENSILE-YIELD, MPa                                                                              0.00    100.94  78.61 0.00                                  ELONGATION @ BREAK %                                                                            2.29    6.70    127.30                                                                              1.12                                  TENSILE-MODULUS, GPa                                                                            6.42    5.75    5.10  5.22                                  TENSILE-IMPACT, kJ/m2                                                                           101.99  93.79   219.34                                                                              13.59                                 DYNATUP IMPACT    1.82    2.19    2.96  1.56                                  STRENGTH, J                                                                   NOTCHED IZOD @ 0° C. J/m                                                                 20.83   22.43   19.22 10.68                                 NOTCHED IZOD @    18.16   24.56   22.43 9.61                                  23° C. J/m                                                             UNNOTCHED IZOD @          432.01  504.10                                                                              71.56                                 23° C. J/m                                                             DTUFL (1.8 MPa, 2° C./min.)                                                                      81.00   64.65 75.65                                 (unannealed) °C.                                                       DTUFL (1.8 Mpa, 2° C./min.)                                                                      95.80   67.80 76.25                                 (ann. 4 hrs. @ 80° C.), °C.                                     ______________________________________                                    

Examples 91-99

The examples described in TABLE XII are illustrative of the efficacy ofthe acrylic-modified PVOH as a hot melt adhesive. The composition ofeach example is given in weight percent. The particular PVOH polymersused in the examples were obtained from AIR PRODUCTS (AIRVOL) and DuPont(ELVANOL). The polymers are as follows: AIRVOL-107 is a fully hydrolyzed(98.0-98.8 mol %) resin having a solution viscosity of 5.4-6.5 cPsdetermined on a 4% aqueous solution at 20 ° C. The molecular weight ofthis polymer is Mw=31-50k. ELVANOL-5105 is a low solution viscosity (5-6cPs), gel resistant, partially hydrolyzed (87-89 mol %) PVOH resin. Theacrylic terpolymer was prepared from commercially available monomers(MMA, EA and MAA) by emulsion polymerization and isolated by spraydrying or coagulation.

As a comparative example, the adhesive composition, listed in TABLE I asexample 91, was prepared from a powder blend, which comprised of thefollowing ingredients: PVOH, 0.66% (based on the weight of PVOH) of a 85weight percent H₃ PO₄ aqueous solution, and 0.5 weight percent ofIrganox-1010. The free flowing powder was melt compounded in a singlescrew extruder at temperatures ranging from 180°-193° C. andsubsequently pelletized. The adhesiveness of the alloy was evaluated byre-melting the pellets in the extruder employed in the melt compoundingstep and applying the molten resin between the overlapping surface oftwo strips of card board to form a single lap joint. The tensilestrength of the joint was tested by ASTM D3932-80 method. The stripswere pulled on a Zwick tensile tester at a rate of 5.5 inches perminute. The observed adhesion is the pound force per inch (lbf/in) orNewton per meter (N/m) required to pull the lap joint apart. Example 91demonstrates the efficacy of acid neutralized PVOH as a hot meltadhesive. However, it was observed that the thermal stability of theunmodified PVOH was inferior to that of the acrylic modified PVOH.

The adhesive compositions defined as examples 92-95 were prepared by thetechnique described in the comparative example, 91. They illustrate thataddition of the acrylic terpolymer to the PVOH resin improves theadhesiveness of the PVOH-Acrylic alloys. The data listed in TABLE XIIshow a small decrease in tensile strength, compositions 92 and 93, withan increase in the level of acrylic terpolymer. Example 95 shows that analloy comprised of equal weights of the specified acrylic terpolymer andglycerol appears to exhibit slightly higher tensile strength than alloyswithout glycerol.

Examples 96-99, TABLE XII, illustrate the use of hot melt adhesivecompositions prepared from hot water soluble PVOH and an acrylicterpolymer. The adhesive compositions were prepared as previouslydescribed in the comparative example. The performance of compositions96-99 was tested by the standard lap joint formation (ASTM D 3932-80)between two strips of cardboard. As can be seen from the data presentedin TABLE XII, the presence of glycerol appears to improve the strengthof the cardboard lap joint. The low numbers obtained for compositions 96through 99 attest to poor bond formation, on account of the rapidcrystallization of the acrylic modified PVOH alloy. It was observed thatadhesion failure occurred at the substrate face in contact with the airquenched molten adhesive. The bond formed from the initial contactbetween the hot melt and the surface of the substrate was found to beresistant to interfacial delamination. Hence, it should be concludedthat the strength of the lap joint was a function of the method ofapplication of the hot melt.

For the purpose of comparison lap joints were prepared from a commercialhot melt adhesive and ten pairs of cardboard strips. These samples weretested by ASTM D3932-80 and an average adhesion of 65.4 lbf/inch wasrecorded. From TABLE XII it can be seen that the acrylic modified PVOHhot melt adhesive compositions compare favorably in adhesion with thecommercial hot melt adhesive.

                                      TABLE XII                                   __________________________________________________________________________    Hot Melt Formulation Applied to Card Board                                                   EXAMPLES                                                       POLYMER/COMPOSITION                                                                          91 92 93 94 95 96 97 98 99                                     __________________________________________________________________________    ELVANOL-5105   100                                                                              95 93.5                                                                             90 87                                                 AIRVOL-107                    95 93.5                                                                             90 87                                     GLYCEROL       00 00 00 5  6.5                                                                              00 00 5  6.5                                    P(MMA-EA-MAA = 00 5  6.5                                                                              5  6.5                                                                              5  6.5                                                                              5  6.5                                    81/18/01)                                                                     ADHESION       54.1                                                                             69.5                                                                             65.0                                                                             66.6                                                                             71.1                                                                             17.0                                                                             23.9                                                                             35.8                                                                             37.5                                   (lbf/inch)                                                                    __________________________________________________________________________

We claim:
 1. A hot melt adhesive for the bonding of paper, wood, andother cellulosic articles comprising a melt-processed polymeric blendof:a) from about 90 parts to about 98 parts of at least one firstpolymer containing at least about 50 mol % units of the structure##STR43## and optionally units selected from one or more of thefollowing structures: ##STR44## wherein R is alkyl, R₁ is H or CH₃, andR₂ is an alkyleneoxy or a C₁ to C₄ alkyl group; and b) from about 2 toabout 10 parts of at least one second polymer containing from about 90to about 98 weight percent of units of at least one structure ##STR45##where R₃ is at least one lower alkyl of from 1-4 carbon atoms, and fromabout 2 to about 10 weight percent of one or more units derived from anunsaturated copolymerizable carboxylic acid or anhydride, the total ofunits derived from (i) and (ii) being 100 %.
 2. The hot melt adhesive ofclaim 1 wherein the optional unit of the at least one first polymer is##STR46## R₁ and R₃ are --CH₃, and the at least one unsaturatedcopolymerizable unsaturated acid has at least one of the followingstructures: ##STR47## where R₄ is --COOH.
 3. The hot melt adhesive ofclaim 1 wherein the second polymer contains both a lower alkyl acrylateand methyl methacrylate.
 4. The hot melt adhesive of claim 1 wherein thesecond polymer further contains up to 5 weight percent of units havingan adhesion-promoting functionality other than a lactam, amide, or acidfunctionality.
 5. The melt processable hot melt adhesive of claim 1further containing up to about 20 parts of a plasticizer.
 6. The hotmelt adhesive of claim 5 wherein the plasticizer is at least one polyol.7. The hot melt adhesive of claim 6 wherein the at least one polyol ispolyethylene glycol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediolor glycerol.
 8. The hot melt adhesive of claims 1 or 5 wherein the firstpolymer has been washed or treated with phosphoric acid to lower thelevel of sodium acetate to below about 0.1 weight percent.